Suspension having magnetic head assembly mounted thereon and magnetic recording disk drive using the suspension

ABSTRACT

A suspension having a magnetic head assembly  1  mounted thereon is provided, wherein the magnetic head assembly comprises: a write head  1 - 2 ; a read head  1 - 1 ; and a resistive heating element  1 - 3  for controlling the flying heights of the magnetic heads, wherein the wires HTx and GTx for the resistive heating element is disposed such that they sandwich the wires RxX and RxY for the read head. The wires for the resistive heating element may be disposed between the wires for the write head and the wires for the read head. Furthermore, the waveform of the current or voltage to the resistive heating element has a time constant of 1 μsec or more, the resistive heating element having wires disposed near the wires of the read head.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese application No.2002-361225, filed Dec. 12, 2002, the entire disclosure of which isincorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to controlling the flying height of a magneticrecording disk drive; and, more specifically, the invention relates topreventing a crosstalk against the read head.

A conventional magnetic recording disk drive (hereinafter referred to asHDD) comprises a head/disk assembly that is a mechanical system, and apackage substrate (PCB) made of circuits. FIG. 13 shows theconfiguration of a head/disk assembly (HDA) 100. The HDA 100 comprisescomponents such as: a magnetic recording disk 2 installed in a chassis(base) 8 through a spindle 5; a magnetic head assembly 1 mounted on thetip of a suspension 3 connected with an actuator 4 driven by a voicecoil motor (VCM) 7; a flexible printed cable (FPC) 6-3 having mountedthereon a read/write IC (R/W IC) 11 which electrically drives themagnetic head assembly 1. The actuator 4 moves the magnetic headassembly 1 so as to position it at an arbitrary location while themagnetic disk 2 is being rotated at a constant speed before thewrite/read operation begins.

FIG. 14 shows how the magnetic head assembly 1 is suspended above themagnetic recording disk 2 in a read/write operation. Due to increasingrecording density of a magnetic recording disk drive, reduced flyingheight of the magnetic head is required. With a reduced flying height,however, the write head element (WRT) 1-2 or the read head element (RD)1-1 is likely to collide with a small bump 51 with a height of a fewnanometers. These bumps are formed due to, for example, the surfaceroughness of the magnetic recording disk 2.

The flying height of the magnetic head assembly above the magneticrecording disk 2 is set to a small value, for example no more than 20nm, in recent years. Assume that the small bump 51 has collided with theread head element (RD) 1-1. In such a case, if the RD 1-1 is amagnetoresistive head (hereinafter referred to as an MR head), theelement produces heat and thereby an abnormal signal is generated by athermal asperity (hereinafter referred to as TA) event. Such an incidentresults in a read abnormality. Further, when a high-frequency writecurrent of a few hundred megahertz flows through the write head element(WRT) 1-2, the element produces heat and thereby the rear end of themagnetic head assembly projects toward the disk surface, as indicated bythe broken lines in the figure. The higher the frequency of thehigh-frequency current, the larger the projection amount, reaching a fewnanometers or more, due to the heat produced by the eddy current. With areduced head flying height, a head element of the magnetic head assemblymight be damaged if it protrudes.

FIG. 15 shows wiring (FPC) 6-1 on the suspension 3 for a magnetic headassembly implemented by a prior art that does not use a resistiveheating element HEAT 1-3. A crosstalk current flows through wires RxXand RxY on the RD side due to the high-frequency current flowing throughwires WxX and WxY on the WRT side and the flyback voltage in the writeoperation. The sense current supplied to the read head 1-1 is generallybetween 2 mA and 3 mA, and if the WRT side and the RD side are in closeproximity, the crosstalk current might be as large or larger than thesense current. Since the read sensitivity increases with increasingsense current, the sense current is preferably set as large as possiblewithin the allowable range. Further, at the same time, long lifeduration is required.

However, in case of a crosstalk, the value of the sense current must bereduced. Therefore, the wires on the WRT side are disposed away from thewires on the RD side to reduce the crosstalk current, and therebyincrease the allowable value of the sense current. Also, an alternatingcurrent against the MR element of the read head, which is caused by thecrosstalk current from the WRT side to the RD side leads to a reductionin the life duration of the MR element itself.

One technique used to solve the above problems is to install theresistive heating element HEAT 1-3 near a head element whose flyingheight has been increased beforehand, as shown in FIG. 14. With thisarrangement, the protruding action of the head element due to heat fromthe resistive heating element HEAT 1-3 is rather utilized in order tocontrol the flying height of the head element (see Japanese publishedapplication JPA 5-020635). There are various ways in which thisresistive heating element is used. Generally, however, a current ispassed through the resistive heating element in the read operation so asto reduce the flying height of the head element by using the heatproduced by the resistive heating element. In the write operation, onthe other hand, the current to the resistive heating element isbasically cut off since due to the high-frequency write current flowingin the write operation, heat is already being produced, reducing theflying height. However, an appropriate amount of current may be appliedin a low-temperature environment such as when the equipment is started.Alternatively, a low current may be applied all the time while adjustingits magnitude in order to provide some narrow flying height.

Another proposed prior art technique is to implement a magnetic headassembly which includes a heating magnetic head in addition to the writemagnetic head and the read magnetic head (see Japanese publishedapplication JPA 11-096608). The technique disclosed in Japanesepublished application JPA 11-096608 increases the temperature of arecording portion of the recording medium to a value corresponding tothe write or read temperature in the write or read operation by use ofthe heating magnetic head, making it possible to read from or write tonarrowed tracks.

However, in Japanese published application JPA 5420635, neither thedetailed means nor the circuit configuration for controlling the amountof the generated heat is disclosed.

Furthermore, if new wiring is provided on the FPC 6-1 to supply power tothe HEAT 1-3 in the prior art technique shown in FIG. 15, it may benecessary to reduce the distance between the wires WxX/WxY on the WRTside and the wires RxX/RxY on the RD side. This might result in anincrease in the crosstalk current. Increased crosstalk current leads toreduction of the sense current to ensure adequate head life duration,which is not preferable. Further, the power supplied to the resistiveheating element HEAT 1-3 is a maximum of a few ten milliwatts. Assumingthat the resistance of the HEAT 1-3 is between some ten ohms throughsome hundred ohms, the current and the voltage amount to some tenmilliamperes and a few volts, respectively. Therefore, if the currentsupplied to the HEAT 1-3 is switched on/off while data on a magneticrecording disk or a servo signal is being read, a large crosstalkcurrent flows through the wires on the RD side, which can cause anabnormality in the read operation.

On the other hand, the heating magnetic head described in Japanesepublished application JPA 11-096608 is provided to increase thetemperature of the recording media; it is not intended to control theflying height of the magnetic head. Furthermore, no consideration isgiven to the adverse effect of a crosstalk current against the readmagnetic head, which is caused by switching the current on/off in theheating magnetic head, or by the high-frequency write current of thewrite magnetic head.

SUMMARY OF THE INVENTION

An embodiment of the present invention is directed to a magnetic headassembly which includes a resistive heating element for preventing thehead element from colliding with small bumps on the magnetic recordingdisk surface (preventing the damage to the head element) and reducing TA(which stands for Thermal Asperity). Specifically, the embodiment isdirected to providing a head element and wiring and/or power supplymeans to the resistive heating element which are designed to avoid theadverse effect of the crosstalk current and so on, to the read head.Further, the embodiment of the present invention is directed toproviding a magnetic recording disk drive capable of properly performingread/write operation even when the internal temperature of the magneticrecording disk drive or the temperature of the surroundings change.

To solve the above problems, one embodiment of the present inventionmainly implements the following configurations.

In the embodiment, a suspension having a magnetic head assembly mountedthereon is provided. The magnetic head assembly comprises: a write headfor writing information to a recording medium; a read head for readingthe information from the recording medium; and a resistive heatingelement for controlling flying heights of the write head and the readhead; wherein in wiring from each terminal of the write head, the readhead, and the resistive heating element to the suspension, wires of theresistive heating element are disposed such that they sandwich wires ofthe read head.

According to another aspect of the present invention, there is provideda suspension having a magnetic head assembly mounted thereon, themagnetic head assembly comprising: a write head for writing informationto a recording medium; a read head for reading the information from therecording medium; and a resistive heating element for controlling flyingheights of the write head and the read head; wherein in wiring from eachterminal of the write head, the read head, and the resistive heatingelement to the suspension, wires of the resistive heating element aredisposed between wires of the write head and wires of the read head.

According to still another aspect of the present invention, there isprovided a suspension having a magnetic head assembly mounted thereon,the magnetic head assembly comprising: a write head for writinginformation to a recording medium; a read head for reading theinformation from the recording medium; and a resistive heating elementfor controlling flying heights of the write head and the read head;wherein a waveform of a current or a voltage to the resistive heatingelement has a time constant of 1 μsec or more, the resistive heatingelement having wires disposed near wires of the read head.

With these arrangements, it is possible to avoid the adverse effect of acrosstalk current, etc. on the read head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of the terminal arrangement of amagnetic head assembly according to a first embodiment of the presentinvention.

FIG. 2 is a diagram showing another example of the terminal arrangementof the magnetic head assembly according the first embodiment of thepresent invention.

FIG. 3 is a diagram showing an example of the terminal arrangement of amagnetic head assembly according to a second embodiment of the presentinvention.

FIG. 4 is a diagram showing another example of the terminal arrangementof the magnetic head assembly according to the second embodiment of thepresent invention.

FIG. 5 is a diagram showing the wiring on a suspension according to thefirst embodiment of the present invention.

FIG. 6 is a diagram showing the wiring on a suspension according to thesecond embodiment of the present invention.

FIG. 7 (which includes FIGS. 7(1) and 7(2)) is a diagram showingexamples of the terminal arrangement of a read/write amplifier accordingto the first embodiment of the present invention.

FIG. 8 is a diagram showing the terminal arrangement of a read/writeamplifier according to the second embodiment of the present invention.

FIG. 9 (which includes FIGS. 9(1) and 9(2)) is a diagram showingexamples of the input/output arrangement of a voltage/current supplycircuit for a HEAT (resistive heating element) incorporated in theread/write amplifier according to the first embodiment of the presentinvention.

FIG. 10 is a diagram showing the waveform of the voltage or currentsupplied to a HEAT according to an embodiment of the present invention.

FIG. 11 is a diagram showing a control procedure in read/writeoperations according to an embodiment of the present invention.

FIG. 12 is a diagram showing the entire circuit configuration of amagnetic recording disk drive according to an embodiment of the presentinvention.

FIG. 13 is a diagram showing the configuration of the head/disk assemblyof a prior art magnetic recording disk drive.

FIG. 14 is a diagram showing how a magnetic head having a resistiveheating element is suspended above a magnetic recording disk inread/write operation.

FIG. 15 is a diagram showing the wiring on the suspension for a priorart magnetic head.

The following table includes a description of reference numerals.

1 magnetic head assembly 1-1 read head (RD) 1-2 write head (WRT) 1-3resistive heating element (HEAT) 2 magnetic recording disk 3 suspension4 actuator 5 spindle 6-1 wiring on suspension 7 voice coil motor (VCM) 8chassis (base) 10 interface connector to host apparatus 11 read/writeamplifier (R/W IC) 12 intermediate connector 13 servo signal area 20serial port (Reg_R/W) for R/W IC 21 recording control signal (RD/WRT) ofR/W IC 22 output (read) differential signal (RDX/Y) 23 input (write)differential signal (WDX/Y) 24 positive source (VCC) 25 GND terminal 26negative source (VEE) 28 voltage/current of resistive heating element(Vhx/Ihx) 29 voltage/current supply circuit (HDV) for resistive heatingelement 31 random access memory (RAM) 32 hard disk controller (HDC) 33digital signal processor (DSP) 34 microprocessor (MPU) 37 buffer RAM(BRAM) 38 read channel IC (RDC) 40 nonvolatile solid-state memory (FROM)50 head select control signal (HD_SEL) within R/W IC 51 small bump onmagnetic recording disk 52 capacitor (Chx) 53 data read control (DataRD) 100 head/disk assembly (HDA) 200 package board (PCB) 300 hostapparatus

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Description will be made below of devices for controlling the flyingheight of a magnetic head according to preferred embodiments of thepresent invention with reference to FIGS. 1 to 12. First of all, generaldescription will be made of a magnetic recording disk drive whichimplements a technique for controlling the flying height of a magnetichead according to an embodiment of the present invention with referenceto FIG. 12. The magnetic recording disk drive (HDD) comprises ahead/disk assembly (HDA) 100 and a package board (PCB) 200, and isconnected to a host apparatus 300.

General servo control operation is described with reference to FIG. 12.A signal read from a servo signal area 13 by the magnetic head elementwithin the HDA 100 is amplified by a read/write amplifier (R/W IC) 11before it is subjected to servo demodulation by the servo demodulationcircuit of a read channel IC (RDC) 38 on the PCB 200 for servodemodulation and data read/write signal processing. Based on thedemodulation results, a digital signal processor (DSP) 33 determines theposition of the magnetic head assembly and reports it to amicroprocessor (MPU) 34. The DSP 33 precisely controls the rotation ofthe motor (not shown) through a combination driver (COMB) 39 and alsocontrols the current in a voice coil motor (VCM) 7 of an actuator 4based on an instruction from the MPU 34 so as to control a seekoperation between tracks of a magnetic recording disk 2 or a trackfollowing operation.

Next, general data read/write control operation is described. The MPU 34issues an instruction to the DSP 33 and a hard disk controller (HDC) 32based on control (information) 14 supplied from the host apparatus 300.After the DSP 33 has positioned the magnetic head assembly at a locationin the recording area (readable/writable area) in the above describedmanner based on the issued instruction, the HDC 32 instructs the RDC 38and the R/W IC 11 to perform read/write control in a sequence stored ina nonvolatile solid-state memory (FROM) 40. In the write operation, theHDC sends the value (user data 15) stored in a buffer RAM (BRAM) 37 tothe RDC 38 after adding error correction code (ECC), etc. to it. The RCD38 performs write signal processing to output serial data to R/W IC 11.The R/W IC 11 converts the data into a write current which is thenconverted to a write magnetic field by the magnetic head element so asto write the data in a predetermined data area of the magnetic recordingdisk 2. In the read operation, the R/W IC 11 amplifies a magnetizationsignal read by the magnetic head element at a predetermined location.The RDC 38 demodulates the magnetization signal into digital data whichis then checked by the HDC 32 to determine whether it contains an error.If it does, the HDC 32 corrects the error before storing the data in theBRAM 32, and reports it to the host apparatus 300.

Description will be made below of a specific configuration of a devicefor controlling the flying height of a magnetic head according to afirst embodiment of the present invention with reference to theaccompanying drawings. FIG. 1 is a diagram showing an example of theterminal arrangement of a magnetic head assembly according to the firstembodiment of the present invention, while FIG. 2 is a diagram showinganother example of the terminal arrangement of the magnetic headassembly according to the first embodiment of the present invention.

As used in this specification and the accompanying drawings, the term“magnetic head assembly 1” refers to a magnetic head assembly whichcomprises the read head (RD) 1-1, the write head (WRT) 1-2, and theresistive heating element (BEAT) 1-3; the term “head element” refers tothe transducer for the read head 1-1 or the write head 1-2; and the term“magnetic head” refers collectively to the read head 1-1 and the writehead 1-2. It should be noted that the magnetic head assembly 1 is notconfigured as an assembly unit. The magnetic head assemblies shown inFIGS. 13 to 15 and those generally used in a head/disk assembly (HDA)are examples of the magnetic head assembly 1.

FIG. 1 shows how each terminal of the magnetic head assembly is“extracted”, and the arrangement of the wires in the wiring (FPC) 6-1 onthe suspension. Reference numeral RD 1-1 denotes a read head which usesa thin-film magnetoresistive element as its head element, whilereference numeral WRT 1-2 denotes a wire-wound write head which uses athin film of a magnetic material and a thin-film conductor as itsmagnetic core and coil, respectively. Furthermore, a resistive heatingelement (HEAT) 1-3 of approximately 100 ohms is provided in the magnetichead assembly 1 to control the flying height. One way of using theresistive heating element is to supply a current of appropriatemagnitude to the resistive heating element in the read operation toreduce the (head) flying height and thereby improve the read sensitivityfor high density recording. A current of appropriate magnitude may alsobe supplied to the resistive heating element in the write operation toreduce the flying height. FIG. 11, described later, shows how to supplya current to the resistive heating element in both the read and thewrite operations.

The power terminals (HTx and GHx) for the HEAT 1-3 are provided on thecentral part of the rear end face of the magnetic head assembly 1. Thewire to be connected to the GHx terminal is disposed on the “magnetichead assembly 1” side such that the wires to the terminals HTx and GHxsandwich the wires RxX and RxY for the RD. As a result, there are 4wires on the RD side and 2 wires on the WRT side.

In FIG. 2, the terminal arrangement of the magnetic head assembly 1 ischanged such that the wire to the GHx terminal of the HEAT 1-3 need notbe disposed on the “magnetic head assembly 1” side. Specifically, thehead terminals for the HEAT themselves sandwich the head terminals forthe RD.

Both configurations shown in FIGS. 1 and 2 implement the same wirearrangement for the wiring (FPC) 6-1 on the suspension except for theportion of the wiring near the magnetic head assembly 1; the (wires) HTxand GHx are disposed such that they sandwich the wires RxX and RxY forthe RD. Furthermore, the wires for the RD are disposed away from thewires for the WRT, making it possible to prevent occurrence of crosstalkfrom the WRT wiring to the RD wiring (if the crosstalk occurs, acrosstalk current flows through the MR element from the WRT wiring tothe RD wiring, which leads to a reduction in the life of the MRelement).

FIG. 5 shows the wiring (FPC) 6-1 on the suspension. The wiring from themagnetic head assembly 1 takes two routes, the RD/HEAT route and the WRTroute, on the suspension 3. They are put together into a single route ata position near the fixed arm end 3-1 of the suspension 3 and furtherextended to a terminal 6-2. The arrangement of the wires in the wiring6-1 shown in the cross-sectional view of FIG. 5 is the same as thoseshown in FIGS. 1 and 2 and can be implemented by a single-layer flexiblewiring cable (FPC).

As shown in detail in FIG. 5, the wire GHx for the HEAT is laid betweenthe wire WxY for the WRT and the wire RxX for the RD and therebyfunctions as a shield. This arrangement considerably reduces theinfluence on the wires RxX and RxY of a flyback generated on the wiresWxX and WxY in the write operation. Since substantially no crosstalkcurrent flows to the RD, it is possible to increase the sense current,thereby enhancing the sensitivity. Thus, the wires for the HEAT sandwichthe wires for the RD, setting the wires for the RD away from the wiresfor the WRT.

FIG. 7 (which includes FIGS. 7(1) and 7(2)) is a diagram showingexamples of the terminal arrangement of a read/write amplifier accordingto the first embodiment of the present invention. FIG. 7(1) shows thecontrol signals Reg_R/W and RD/WRT, the input/output (read/write)differential signals RDX/Y and WDX/Y, the magnetic head drive terminalsRxX/Y, WxX/Y, and HTx/GHx, and the sources VCC, GND, and VEE of aread/write amplifier R/W IC 11. Referring to FIG. 12, the terminalarrangement on the right in FIG. 7(1) is connected to the magnetic headassembly, while that on the left is connected to the PCB.

The example of the R/W IC 11 shown in FIG. 7 handles two magnetic heads(H#0, H#1). However, the present embodiment can be applied to aread/write amplifier handling a larger number of heads such as 4 headsor 8 heads, or even 10 heads. Reference numeral Reg_R/W 20 denotes aserial port which is directly connected to an internal register andcontrolled by the DSP 33 and the RDC 38 shown in FIG. 12. The serialport is made of general control lines such as SDEN, SCLK, and SDATA, andselects each magnetic head using a select signal HD_SEL 50 (see FIG. 11described later) and controls the write and the sense currents of eachhead and the current/voltage, etc. of the HEAT 1-3 for each head throughinternal registers.

FIG. 7(2) shows an example of the R/W IC 11 of IC package typeimplementing a reduced number of pins. The (terminals) GH0 and GH1 shownin FIG. 7(1) are replaced by a single (terminal) GH. Wiring wires on theundersurface of the R/W IC 11 as indicated by the broken line in thefigure realizes the arrangement of the magnetic head drive terminalsshown in FIG. 7(1) only using a single-layer FPC. For 4-head and 8-headR/W ICs 11, all of the 4 terminals GH0 to GH3 may be replaced by asingle terminal.

FIG. 9 (which includes FIGS. 9(1) and 9(2)) shows examples of theinput/output arrangements of a voltage/current supply circuit (HDV) 29for the HEAT incorporated in the R/W IC 11. The HDV 29 can beimplemented by a general programmable voltage source or current source.Whether the system is driven by a voltage source or current source maybe determined beforehand and only one of the sources (circuits) may beimplemented. Or alternatively, both sources (circuits) may beincorporated and it may be arranged such that the mode can be set by useof an internal register. The magnitude of the power to be supplied tothe HEAT is approximately 50 mW or less. Therefore, assuming that theresistance of the heating element is 100 ohms, the voltage/currentsupply circuit can be implemented by a voltage source of between 0 V and2.5 V or a current source of between 0 mA and 25 mA. A resolution of 3or 4 bits (8 to 16 levels) is generally enough for setting thevoltage/current. With the sources VCC, GND, and VEE connected to thecircuits, an internal register incorporated in the R/W IC issues an SELx(signal) to independently turn on/off the HDV 29 for each head. At thattime, the voltage/current values are controlled by the Vhx/Ihx (signals)sent from an internal register. In the example shown in FIG. 9(2), theGHx is replaced by a (single terminal) GH, as in FIG. 7(2).

FIG. 10 shows the waveform of the voltage or the current supplied fromthe HDV 29 shown in FIGS. 9(1) and 9(2) to the HEAT. In the case of thevoltage source, for example, if Vhx 28 is set to between 0 V and 1.5 V,the voltage supplied through the HTx terminal increases relativelygradually with a time constant Tr of 1 μsec or more (corresponding to afrequency of 150 kHz or less). Then, if Vhx 28 is set to 0 V, thevoltage decreases relatively gradually to 0 V with a time constant Tf of1 μsec or more. This arrangement can be easily implemented by a generalprogrammable voltage source or current source and taking into accountthe CR change/discharge time constant. Furthermore, an active low-passfilter (LPF) having a cutoff frequency of approximately 150 kHz may beprovided at the voltage/current output stage to obtain a similar outputwaveform, instead of implementing a programmable voltage source orcurrent source.

Description will be made of the reason why the time constant is set to 1μsec or more. The read band of the R/W IC 11 generally ranges from 500kHz. Since 1 μsec corresponds to 150 kHz, a HEAT voltage waveform of 150kHz, which is lower than the lower frequency limit 500 kHz of the readsignal, does not adversely affect the read signal very much even in theread operation. Therefore, when an instantaneous crosstalkvoltage/current is produced from the HEAT wiring to the RD wiring due toswitching of voltage/current values to the HEAT during a data or servosignal read operation, the above means can be used to prevent itsinfluence on the subsequent stages of the R/W IC 11. Certainly, it ismore desirable to avoid switching voltage/current values of the HDV 29during a data or servo signal read operation.

The voltage/current waveform in FIG. 10 described above is establishedbased on the first embodiment in which the wires for the HEAT sandwichthe wires for the RD. However, this waveform is not limited to the firstembodiment. The voltage/current waveform shown in FIG. 10 is effectivein any case where the HEAT wiring and the RD wiring coexist and acrosstalk current is produced from the HEAT wiring to the RD wiring. Theadoption of this waveform itself constitutes an embodiment of thepresent invention.

FIG. 11 shows a procedure for controlling the HEAT in read/writeoperations. Description will be made of the control operation performedwhen the magnetic head H#1 carries out a write operation in a relativelyshort time after data is read with the magnetic head H#0.

The HD_SEL 50 (signal) issued from an internal register of the R/W IC 11is currently set to “H#1” to indicate selection of the H#1. In thisstate, Vh0 (28-0) is set to 1.5 V and the value of HD_SEL 50 is changedto “H#0” 3 msec or more before the data read operation begins. After themagnetic recording disk has rotated to a desired read position, the HDCshown in FIG. 12 instructs the RDC 38 to perform data read control (DataRD 53). Then, Vh1 (28-1) is set to 1.7 V at some point during the aboveoperation 3 msec or more before the data write operation with the H#1begins. After the data read operation with the H#0 has been completed,the HD_SEL 50 is set to “H#1”. After the magnetic recording disk hasrotated to a desired write position, the information sent on the dataWDX/Y (signal) from the RDC 38 is written under control of the DSP 33using the RD/WRT 21 (signal).

At that time, if the write current is continuously supplied to the writehead H#1, the flying height is further reduced due to the heat from thewrite head Therefore, Vh1 (28-1) is set to 0.5 V at an appropriatetiming to reduce the amount of heat generated in the HEAT so as toprevent the flying height from being excessively reduced. It should benoted that in the above arrangement, power is supplied to the HEAT for 3msec or more before the read or write operation. However, since adifferent length of time may be more appropriate depending on the timeconstant (τh) for the heat distortion of the magnetic head, the positionand shape of the heating element, and the materials of each component ofthe magnetic head, the length of time is preferably determined for eachmagnetic head type. It is arranged such that in the above operation, Vh0and Vh1 can be driven at the same time. Thus, the above control methodcan compensate for the time constant for the heat distortion of themagnetic head.

Let Hfm denote the flying height margin to be provided (if the flyingheight does not exceed Hfm, there is a risk of the head elementcolliding with the disk). Then, determine, through tests of eachmagnetic head, (1) the relation between the flying height and theambient temperature when no write operation is performed and no power issupplied to the HEAT (expressed as Hf(T)), and further determine (2) theamount of reduction of the flying height due to the write current of thewrite head (expressed as ΔHw (Iw)) and (3) the relation between thesupply voltage to the HEAT and the amount of reduction of the flyingheight due to the heat from the HEAT (expressed as ΔHh(Vh)). Then, therelation ΔHh(Vh) may be controlled for each ambient temperature suchthat the following inequality holds.Hf(T)−(ΔHw(Iw)+ΔHh(Vh))>Hfm

Strictly speaking, Hfm and ΔHw (Iw) may be replaced by Hfm(r) and ΔHw(Iw, fw), considering the dependence of the flying height on themagnetic recording disk radius r and the write frequency fw,respectively, which results in the following inequality.Hf(T)−(ΔHw(Iw,fw)+ΔHh(Vh))>Hfm(r)

The timing at which the supply voltage (Vh) to the HEAT is switched fromone value to another is set such that the switching operation isperformed the time corresponding to the time constant for the heatdistortion of the magnetic head (τh) or longer before the write or readoperation is expected to begin. This arrangement makes it possible toperform read/write operation with an accurately compensated flyingheight.

Description will be made below of a specific configuration of a devicefor controlling the flying height of a magnetic head according to asecond embodiment of the present invention with reference to theaccompanying drawings. FIG. 3 is a diagram showing an example of theterminal arrangement of a magnetic head assembly according to the secondembodiment of the present invention, while FIG. 4 is a diagram showinganother example of the terminal arrangement of the magnetic headassembly according to the second embodiment of the present invention.The second embodiment is different from the above first embodiment inthe method for “extracting” each terminal of the magnetic head assembly,the arrangement of the wires on the suspension, and the pin arrangementand configuration of the read/write amplifier (R/W IC).

FIG. 3 shows how each terminal of the magnetic head assembly 1 is“extracted”, and the arrangement of the wires in the wiring (FPC) 61 onthe suspension. In the magnetic head assembly 1, reference numeral RD1-1 denotes a read head which uses a thin-film magnetoresistive elementas its head element, while reference numeral WRT 1-2 denotes awire-wound write head which uses a thin film of a magnetic material anda thin-film conductor as its magnetic core and coil, respectively. Aresistive heating element (HEAT) 1-3 of 100 ohms is provided to controlthe flying height. The power terminals (HTx and GHx) for the HEAT 1-3are provided on a side part (not the central part) of the rear end faceof the magnetic head assembly 1. There are 4 wires on the RD sideincluding the wires for the HEAT, and 2 wires on the WRT side.

In FIG. 4, the terminals HTx and GHx for the HEAT 1-3 are each disposedon a respective side part of the magnetic head assembly 1. As a result,there are 3 wires on each of the RD side and the WRT side.

Both configurations shown in FIGS. 3 and 4 implement the same wirearrangement for the wiring (FPC) 6-1 on the suspension except for theportion of the wiring near the magnetic head assembly 1; the (wires) HTxand GHx for the HEAT are laid such that the wires RxX and RxY for the RDare disposed away from the wires WxX and WxY for the WRT. That is, thesecond embodiment shown in FIGS. 3 and 4 is different from the firstembodiment in that the first embodiment sandwiches the wires for the RDbetween the wires for the HEAT whereas the second embodiment disposesthe wires for the RD away from the wires for the WRT and lays the wiresfor the HEAT therebetween functioning as a shield.

FIG. 6 shows the wiring (FPC) 6-1 on the suspension. The wiring from themagnetic head assembly 1 takes three routes, the RD, the HEAT, and theWRT routes, on the suspension 3. They are put together into a singleroute at a position near the fixed arm end 3-1 of the suspension 3 andfurther extended to a terminal 6-2. The arrangement of the wires in thewiring 6-1 shown in the cross-sectional view of FIG. 6 is the same asthose shown in FIGS. 3 and 4 and can be implemented by a single-layerflexible wiring cable (FPC). As shown in FIG. 6, the two wires for theHEAT are laid between the wires for the WRT and the wires for the RD andfunction as a shield and increase the distance between the wires for theWRT and the wires for the RD. This arrangement reduces the influence onthe wires RxX and RxY of the flyback generated on the wires WxX and WxYin the write operation much more than the first embodiment does. Sincesubstantially no crosstalk current flows to the RD, it is possible toincrease the sense current and thereby enhance the sensitivity.

FIG. 8 shows the control signals Reg_R/W and RD/WRT, the input/output(read/write) differential signals RDX/Y and WDX/Y, the magnetic headdrive terminals RxX/Y, WxX/Y, and HTx/GHx, and the sources VCC, GND andVEE of a read/write amplifier R/W IC 11. According to the secondembodiment, a capacitor (Chx) 52 of a few nanofarads is provided betweenthe HTx and the GHx to produce a time constant for the current of theHEAT shown in FIG. 10. Therefore, the HDV 29 within the R/W IC 11 shownin FIG. 9 need not provide any time constant. However, in the above casewhere the capacitor Chx is installed, the HEAT cannot be powered byvoltage. Only a current control can be used. This is because thetransient current flowing in the capacitor Chx cannot be controlledthrough a voltage control. Therefore, “Vh” in FIG. 11 must be replacedby “Ih” when the figure is applied to a control procedure for read/writeoperation according to the second embodiment.

As described above, the present invention relates to a magnetic head ofa magnetic recording disk drive, wherein the magnetic head is made of awrite head (WRT), a read head (RD), and a resistive heating element(HEAT). In connection with the magnetic head, the present inventionprovides the following configuration examples (first to fifth examples).According to a first example, the magnetic head has 6 terminals for thewrite head, the read head, and the resistive heating element, whereinthe wires on the resistive heating element side are disposed such thatthey sandwich the wires on the read head side. This arrangement allowsthe wires on the resistive heating element side to prevent a crosstalkcurrent from being induced from the wires on the write head side to thewires on the RD side in the write operation. Further, according to asecond example, the wires on the resistive heating element side aredisposed between the wires on the write head side and the wires on theread head side. This arrangement also allows the wires on the resistiveheating element side to prevent a crosstalk current from being inducedfrom the wires on the write head side to the wires on the RD side.

Still further, according to a third example, the read/write amplifierincludes a programmable current source or voltage source for supplyingpower to the resistive heating element. This arrangement makes itpossible to compensate for the variations in the flying height due tovariations in the manufacturing process of the magnetic head, theambient temperature, etc. by controlling the amount of heat generated inthe resistive heating element. Still further, according to a fourthexample, the programmable current source or voltage source of the thirdexample switches between current values or voltage values with a timeconstant of 1 μsec or more. Still further, according to a fifth example,in the programmable current source or voltage source of the thirdexample, a capacitor of a few nanofarads is provided across the outputterminals of means for switching between stepwise current values.Furthermore, the present invention also relates to a method forcontrolling a magnetic recording disk drive. In this connection, thepresent invention provides the following configuration examples (sixthto eleventh examples). According to a sixth example, the current sourceor voltage source of the third example performs no switching operationduring a data or servo signal read operation.

Further, a seventh example includes: means for, through tests of eachmagnetic head, determining and storing the relation between the flyingheight and the ambient temperature T when no write operation isperformed and no power is supplied to the resistive heating element(expressed as Hf(T) in which the flying height margin to be provided isdenoted by Hfm); means for storing the amount of reduction of the flyingheight due to the write current Iw of the write head (expressed as ΔHw(Iw)); means for storing the relation between the supply voltage to theresistive heating element and the amount of reduction of the flyingheight due to the heat from the resistive heating element (expressed asΔHh(Vh)); and means for measuring the ambient temperature T; wherein thesupply voltage Vh to the resistive heating element is controlled basedon the ambient temperature T and the read/write conditions such that thefollowing inequality holds: Hf(T)−(ΔHw(Iw)+ΔHh(Vh))>Hfm. Still further,according to an eighth example, Hfm and ΔHw (Iw) in the seventh exampleare replaced by Hfm(r) and ΔHw (Iw, fw), considering the dependence ofthe flying height on the magnetic recording disk radius r and the writefrequency fw, wherein the supply voltage Vh to the resistive heatingelement is controlled based on the ambient temperature T and theread/write conditions such that the following inequality holds:Hf(T)−(ΔHw(Iw,fw)+ΔHh(Vh))>Hfm(r).

Still further, according to a ninth example, the seventh or eighthexample is further configured such that the supply of the current orvoltage (Vh/Ih) to the resistive heating element is initiated the timecorresponding to the time constant for the heat conductance of themagnetic head or longer before the read/write operation begins. Stillfurther, according to a tenth example, the read/write amplifier includesa programmable current source or voltage source for supplying power tothe resistive heating element of the magnetic head. Still further,according to an eleventh example, the tenth example is furtherconfigured such that the programmable current source or voltage sourceswitches between current values or voltage values with a time constantof 1 μsec or more.

Furthermore, the present invention also relates to a suspension,providing the following configuration examples (twelfth and thirteenthexamples). According to a twelfth example, the suspension has mountedthereon a magnetic head having 6 terminals for a write head, a readhead, and a resistive heating element, wherein the wires on theresistive heating element side are disposed such that they sandwich thewires on the read head side. Further, according to a thirteenth example,the suspension has mounted thereon a magnetic head having 6 terminalsfor a write head, a read head, and a resistive heating element, whereinthe wires on the resistive heating element side are disposed between thewires on the write head side and the wires on the read head side.Furthermore, according to a fourteenth example, the read/write amplifierfor the magnetic recording disk drive in the tenth example is configuredsuch that it can drive two or more programmable current sources orvoltage sources at the same time.

The above-described preferred embodiment relates to a magnetic headassembly which includes a resistive heating element for preventing thehead element from colliding with small bumps on the magnetic recordingdisk surface (preventing damage to the head element) and reducing TA.The present invention can avoid the adverse effect on the read head ofthe crosstalk current, etc. due to the high-frequency current of thewrite head or switching on/off of the current in the resistive heatingelement by: sandwiching the wires for the read head between the wiresfor the resistive heating element; disposing the wires for the resistiveheating element between the wires for the read head and the wires forthe write head; or configuring the power supply source to the resistiveheating element such that it has an appropriate time constantFurthermore, the present invention provides a magnetic recording diskdrive capable of properly performing read/write operation even when theinternal temperature of the magnetic recording disk drive or an ambienttemperature such as the outside air temperature changes.

1. A head gimbal assembly comprising: a write element for writinginformation to a recording medium; a read element for reading saidinformation from said recording medium; a heating element forcontrolling flying heights of said write element or said read element;1st and 2nd wirings for electrically connecting to said read element;3rd and 4th wirings for electrically connecting to said write element;5th and 6th wirings for electrically connecting to said heating element;and a suspension having said 6 wirings; wherein one of the 5th or the6th wiring electrically connects the ground, and wherein said 5th or 6thwiring that connects to ground is disposed between 1st and 2nd wiringsand 3rd and 4th wirings on said suspension.
 2. The head gimbal assemblyof claim 1 further comprising: 1st and 2nd terminals for electricallyconnecting to said 1st and 2nd wirings and said read element; 3rd and4th terminals for electrically connecting to said 3rd and 4th wiringsand said write element; 5th and 6th terminals for electricallyconnecting to said 5th and 6th wirings and said heating element; whereinsaid 1st and 2nd terminals are disposed between 5th and 6th terminals intrack width of said magnetic head.
 3. The head gimbal assembly of claim2 wherein said 3rd and 4th terminals are further disposed between 5thand 6th terminals in track width of said magnetic head.